Break biscuits into a food processor or grinder and pulse until fine crumbs are formed. Empty into a bowl.
Add milk a little at a time so the batter starts out stiff. This helps prevent lumps. Add remaining milk and mix well for 1 minute until batter is very smooth. If it is too thick, add a little more milk (it should look like any cake batter).
Oil the bottom and sides of a 7 or 8 inch pot. Line bottom with a piece of parchment paper cut to fit, as well as the sides. Oil the paper also.
Sprinkle baking soda onto batter and add a spoonful of milk on top. Mix into the batter until well incorporated.
Pour batter into prepared pot and place on the lowest setting of stove top. Cover with a tight fitting lid and bake 40 minutes. Do not remove lid until at least 30 minutes cooking. Toothpick inserted in the middle should come out clean.
Cool cake for 5 minutes in the pot, then loosen from the sides and turn out onto a rack. Eat as is or top with your favorite frosting.